Unit price breakdowns in MEP: method and calculation

Behind every unit rate in a bill of quantities sits a calculation. A price breakdown makes that calculation explicit: what the material really costs, what the installation really costs, and what has to be added for the job to be profitable. Here is the method, applied to technical packages.

What a price breakdown is for

A price set by gut feeling is hard to defend. A breakdown serves three very concrete purposes.

• Reliability: once decomposed, an absurd installation time or a forgotten supplier price becomes immediately visible.
• Justification in front of the client, the design team, or during negotiation. A decomposed price can be discussed line by line; a global price can only be accepted or refused.
• Reuse: once built for an item, a breakdown becomes a company asset, reusable from job to job with a simple rate update.

The two components of a price

Everything starts from two kinds of spend, which must always be kept separate.

Material cost covers the equipment itself: pipe, fire damper, duct, switchgear. Start from the supplier list price and apply your negotiated discount. Then add sundries and consumables — clips, fixings, seals, installation products — either as a flat percentage or as a dedicated line.

Labour cost covers installation time, expressed in hours per unit of work, multiplied by the company's hourly rate. Unit times come from your own records or an industry time base; the hourly rate must include the fully loaded employment cost, not the gross wage.

Adding the two gives the net cost: the direct cost of the work, before overheads and before margin.

Getting installation times right

This is where most of the gap between estimate and reality is created. A few markers.

• Unit times must reflect normal site conditions. Specific constraints — occupied buildings, working at height, heavy trade congestion, out-of-hours work — are handled separately, through a coefficient or a cost line, never by quietly inflating times.
• An installation time covers handling at the workface, fitting and routine finishing. It generally excludes design, commissioning and handover: those have their own items.
• Compare theoretical times with actual timesheets regularly. It is the only way the database improves.

From net cost to sell price

Net cost only covers direct spend. Three families of charges sit between it and the sell price.

• Site costs: set-up and removal, supervision, scaffolding and access equipment, lifting, skips and waste removal, power, security. These attach to the job, not to the line.
• Company overheads: management, design office, accounts, premises, insurance, vehicles, IT. These are spread across all activity.
• Risk and profit: the reward for the risk taken and the margin you are aiming for.

Two approaches coexist. Either these charges are added line by line, through a coefficient applied to net cost. Or they are handled globally, as job costs, with a lower coefficient on the lines. The first gives an immediately coherent schedule; the second better reflects how fixed costs actually behave. Many firms combine both: a coefficient per cost type, plus an identified site-cost line.

A worked example

Take one linear metre of black steel pipe installed in a plant room.

• Material: discounted rate of €12.00 per metre, plus 8% sundries → €12.96
• Labour: 1.05 h/m at €42.00/h fully loaded → €44.10
• Net cost: 12.96 + 44.10 = €57.06
• Sell coefficient applied: 1.28 → unit sell price ≈ €73.04

What stands out is the weight of labour: more than 77% of the net cost. On this kind of item, a 10% error on installation time costs far more than a 10% error on the price of the pipe. That is precisely why we decompose.

The errors that come up most often

• Using an unloaded hourly rate. The gap between gross wage and real employment cost turns directly into lost margin.
• Forgetting consumables. Trivial line by line; significant across a whole job.
• Applying the coefficient to the extended total rather than the unit rate, which shifts the rounding and makes the schedule inconsistent.
• Freezing the price database. A database untouched for two years prices at two-year-old rates.
• Never comparing estimated with actual. Without feedback, the same gaps repeat job after job.

In short

A good breakdown separates material from labour, relies on verified installation times, and makes the step from net cost to sell price explicit. Once that mechanism is in place, estimating stops being an exercise in intuition: it becomes a calculation you can explain, defend and improve.